I'm trying to write to Firestore all the prices from different stocks. Structure should look something like this (although this might not be the best fitted for it, still thinking of it as in SQL) :

const d1 = new Date();
const result = d1.getTime();
console.log('Epochtime',result);
database.collection("stock1").doc("exchange1").collection(date).doc('prices').set({"price":"price_value"})

Now the problem is that I can't create a collection with a name that's a variable that contains date. I tried all the different types of it and I presumed that epoch time should work, as this is a number like: 1636213439908. I always get the error: Value for argument "collectionPath" is not a valid resource path. Path must be a non-empty string. Although the exact same variable can be written as a value in a collection. So not sure what am I doing wrong here.